The present invention relates to a ball ramp actuator utilized in a vehicle driveline clutch to supply a clamping force. More specifically, the present invention relates to a ball ramp actuator utilized in a vehicle driveline clutch to supply a clamping force where a secondary armature connected to the engine flywheel is used to lock the ball ramp actuator in position.
Ball ramp actuators have been used in various vehicle driveline components to produce an axial motion in response to a control signal which is used to load a clutch or other friction device. The control signal is used to supply an electrical current to an electrical device such as a coil or a motor which acts to energize the ball ramp actuator by applying a force to a control ring thereby resulting in relative rotational motion between the control ring and an activation ring. The relative motion causes one or more rolling elements to traverse a corresponding number of variable depth ramps formed in the control ring and the activation ring thereby causing the ball ramp mechanism to axially expand. Reference is made to U.S. Pat. Nos. 4,805,486, 5,078,249 and 5,092,825 the disclosures of which are hereby incorporated by reference, for a detailed teaching of the operation of prior art ball ramp mechanisms as used in vehicle driveline components.
One problem with ball ramp mechanisms is that undesirable changes in the degree of activation can occur due to variations in the input and output speeds and torques. This is especially true for ball ramp actuators that connect the control ring to a rotating input element and the activation ring to an output element and thereby use the input power to activate the ball ramp mechanism.
Application USSN: 08/165,684, the disclosure of which is incorporated by reference, discloses such a ball ramp mechanism used in a driveline clutch assembly to axially force the pressure plate against a clutch disc and flywheel.